Additional Resources:

Program Profile: Police Body-Worn Cameras (Washington, D.C.)

Evidence Rating: No Effects - One study No Effects - One study

Date: This profile was posted on April 09, 2019

Program Summary

Police body-worn cameras (BWCs) are designed to improve policing and the perceived legitimacy of the police and legal institutions. The program is rated No Effects. There were no statistically significant differences in police use of force, number of citizen complaints, or number of arrests for disorderly conduct for police officers who wore BWCs, compared with officers who did not wear BWCs.

This program’s rating is based on evidence that includes at least one high-quality randomized controlled trial.

Program Description

Program Goals/Program Components
Police body-worn cameras (BWCs) are designed to improve policing and the perceived legitimacy of the police and legal institutions. One agency that has adopted the use of BWCs is the Metropolitan Police Department of the District of Columbia (MPD). The MPD is one of the largest police departments in the country, with more than 3,800 sworn officers and a resident population of more than 680,000 (Yokum et al. 2017). BWCs are intended to increase positive officer interactions with the community by reducing unprofessional behavior or misconduct, especially unjustified use of force. Similarly, civilians interacting with officers should be less likely to engage in inappropriate or combative behavior if they are aware that the officers are wearing BWCs.

In Washington, D.C., MPD police officers who wear BWCs are required to start their BWC recordings as soon as a call is initiated, via radio or communication from the Office of Unified Communications, on their mobile data computer, or at the beginning of any self-initiated police action. This includes, but is not limited to, all stops and searches, vehicle and foot pursuits, traffic crash scenes, encounters with individuals presenting with mental illness, use-of-force situations, arrests, and encounters requiring officers to advise suspects about their Miranda rights.

When feasible, MPD officers are supposed to inform citizens that they are being recorded at the beginning of any contact. Officers are not supposed to deactivate their BWCs unless they have notified the dispatcher of the assignment’s disposition, concluded their involvement in a citizen contact, or have been ordered to do so by a higher-ranking official, in which case the officers should document the order and the name of the official on the incident or arrest report and on the BWC.

MPD officers are required to upload recorded data from the BWCs to a storage database. Recordings are categorized according to the most serious offense. The categories include, but are not limited to, supervisory review (for any recording that needs to be reviewed by an official), murder/manslaughter, first-and second-degree sexual assault, crime involving a public official (felony or misdemeanor), all other felonies, and all other misdemeanors.

Officers involved in a police shooting may not review their BWC recordings, or other officers’ recordings, related to the case. In all other cases, officers may view their recordings to assist in accurate report writing, testifying in court, for training purposes, and debriefing (MPD 2016). BWC recordings are retained and accessible on the database for a period of 90 calendar days, unless they are specifically categorized otherwise (for example, recordings pertaining to murder/manslaughter are retained for 65 years).

Program Theory
One of the underlying theoretical foundations of police BWCs is deterrence theory, particularly the portion of theory that focuses on certainty of apprehension for wrongdoing (Ariel et al. 2018). BWCs may increase people’s perceived risk of detection or apprehension for wrongdoing because their actions may be caught on camera. This deterrent effect may reduce rule violations or illegal behavior by police, but it may also apply to people with whom they come into contact if those people are aware their behavior is being recorded (Paternoster 2010).

The deterrent effect of BWCs may also be grounded in the Hawthorne effect, which suggests that individuals behave differently when they believe they are being watched. BWCs are therefore anticipated to have a positive effect on the behavior of both police and civilians (Farrer and Ariel 2013).

Evaluation Outcomes

top border
Study 1
Use of Force
Yokum and colleagues (2017) found that there were no statistically significant differences in use of force for officers who wore body-worn cameras (BWCs), compared with officers who did not wear BWCs.

Citizen Complaints
There were no statistically significant differences in the number of citizen complaints for officers who wore BWCs, compared with officers who did not wear BWCs.

Arrests for Disorderly Conduct
There were no statistically significant differences in the number of arrests for disorderly conduct by officers who wore BWCs, compared with officers who did not wear BWCs.
bottom border

Evaluation Methodology

top border
Study 1
Yokum and colleagues (2017) conducted a randomized trial to examine the effects of police body-worn cameras (BWCs) on a large sample of police officers in Washington, D.C. Officers from seven police districts and several specialized units within the Metropolitan Police Department of the District of Columbia (MPD) were randomly assigned to either the treatment group (BWCs) or control group (no BWCs), after meeting the following eligibility criteria: 1) were on active, full-duty administrative status and did not have a scheduled leave of absence during the study period; and 2) held a rank of sergeant or below and were assigned to patrol duties in a patrol district or to a non-administrative role at a police station. The evaluation took place from June 28, 2015, to December 15, 2016, and outcomes were tracked until March 31, 2017.

A total of 2,224 officers participated in the study, with 1,189 officers assigned to the BWC group and 1,035 officers assigned to the control group. The authors used a two-level block randomization assignment in which the “major” blocks were the seven police districts and three special units, and the “minor” blocks were constructed based on the background characteristics of the officers. Officers were grouped into blocks based on pretreatment information. A fixed number of BWCs were then randomly assigned to officers in each block. The BWC group was 82.6 percent male, 54.4 percent black, 33.3 percent white, 7.7 percent Hispanic, 3.2 Asian or Pacific Islander, and 0.2 percent American Indian or Alaska Native. The control group was 82.1 percent male, 51.3 percent black, 35.3 percent white, 9.3 percent Hispanic, and 3.4 percent Asian or Pacific Islander. Both the BWC and control groups had a median length of service of 12 years. There were no significant differences between the groups at the baseline. The BWC group was required to wear and use a BWC in accordance with MPD policy (MPD 2016).

Administrative data were used to assess the effect of BWCs on four sets of outcomes over an 11-month period. The four outcomes included 1) police use of force (self-reported by the officers), 2) civilian complaints, 3) police activity (traffic citations, warnings, reports, and arrests for certain charges), and 4) judicial outcomes. The use of force measure was based on officers’ self-reported use of force and included all force incidents, as well as more specific measures of serious uses of force, other uses of force, and use-of-force incidents by the race of the subject. Civilian complaints included all complaints filed against officers either through the MPD or through the independent Office of Police Complaints, and complaints disaggregated by disposition (sustained, not sustained, or insufficient facts to resolve). Policing activity included traffic tickets and warnings issued, reports from different types of calls for service, arrests on specific charges (e.g., disorderly conduct), and injuries sustained by officers in the line of duty. Judicial outcomes included whether arrest charges were prosecuted and the disposition of those charges. All outcomes were obtained at the officer level and translated into yearly rates. For judicial outcomes, the researchers had access to only a subset of the data, and not the full databases, which limited their ability to conduct all the originally intended analyses. Therefore, these outcomes were not included in the review.

The researchers used two estimators of the average BWCs effect: 1) difference-in-means, with inverse probability weights to account for differential probabilities of assignment by block; and 2) regression of outcome on treatment assignment, with controls for pretreatment characteristics and inverse probability weights. The researchers controlled for the pretreatment value of the outcome (e.g., past use of force), pretreatment covariates for the officer, and indicators for each major block. The study authors did not conduct subgroup analyses.
bottom border


top border
There is no cost information available for this program.
bottom border

Implementation Information

top border
Officers were trained to use the body worn cameras in accordance with Metropolitan Police Department policy. The manual can be found at
bottom border

Evidence-Base (Studies Reviewed)

top border
These sources were used in the development of the program profile:

Study 1
Yokum, David, Anita Ravishankar, and Alexander Coppock. 2017. Evaluating the Effects of Police Body-Worn Cameras: A Randomized Controlled Trial. Washington, D.C.: The DC Lab Working Paper.
bottom border

Additional References

top border
These sources were used in the development of the program profile:

Ariel, Barak, Alex Sutherland, Darren Henstock, Josh Young, and Gabriela Sosinski. 2018. “The Deterrence Spectrum: Explaining Why Police Body-Worn Cameras ‘Work’ or ‘Backfire’ in Aggressive Police–Public Encounters." Policing: A Journal of Policy and Practice 12(1):6–26.

Ariel, Barak, W.A. Farrar, and Alex Sutherland A. 2015. “The Effect of Police Body-Worn Cameras on Use of Force and Citizens’ Complaints Against the Police: A Randomized Controlled Trial.” Journal of Quantitative Criminology 31(3): 509–535.

Farrar, W., and Ariel, B. 2013. Self-Awareness to Being Watched and Socially-Desirable Behavior: A Field Experiment on the Effect of Body-Worn Cameras and Police Use-Of-Force. Washington, D.C.: Police Foundation.

MPD [Metropolitan Police Department of the District of Columbia]. 2016. “Body-Worn Camera Program.” General Order.

Paternoster, Raymond. 2010. “How Much Do We Really Know about Criminal Deterrence.” Journal of Criminal Law and Criminology 100(3):765–24.
bottom border

Program Snapshot

Gender: Both

Race/Ethnicity: Black, American Indians/Alaska Native, Asian/Pacific Islander, Hispanic, White, Other

Geography: Urban

Setting (Delivery): Workplace, Other Community Setting

Program Type: Community and Problem Oriented Policing, Violence Prevention, General deterrence

Current Program Status: Active